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New phones at home..

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I was getting tired of the noise and rubbish quality of the older BT DigitalClarity DECT phones we have been using at home for the last 3 years or so. They were good when we first bought them but quality of the calls has been going down hill.

Some may know (or may not) that I’ve been using VoIP since about Nov 2004. This started off just as a simple end user of some service, but, if you know me at all you’ll know this just isn’t good enough ๐Ÿ™‚ I moved on to using Asterisk (an OpenSource PABX). This has lead to a lot of playing and even training to get my dCAP Certification from Digium, the folks that really maintain Asterisk.

To read more please continue on…

Anyhow, back to the phones. I have just received a Siemens Gigaset C475 IP cordless Voice over IP phone (with answering machine, that will never be used).


This is one very sweet phone system!!! Up until now I’ve been using the aforementioned BT DECT phone (4 hand sets) plugged into a Sipura SPA-3000 ATA. Whoa, hold the phone (pardon the pun) .. “What the hell are you talking about?” .. I know that’s what you’re asking yourself. OK, an ATA is an Analog Telephone Adapter, simply put it turns your bog standard, run of the mill house phone into an all powerful VoIP phone. The SPA-3000 plugs into your telephone jack and your home network, and you plug your normal phone into the box as well. This allows you to make and receive telephone calls both over the Internet and your normal phone company. Anyhow, this box has been and is still working well, it’s the phones that we had that are the problem. Well, there is a problem with this setup.. firstly, we have 4 hand sets dotted around the house, but only one can be used at a time, not a common issue but at times it is.

The new phone, the Siemens Gigaset C475 IP. This is one snazzy phone. It’s a DECT based cordless phone with a built in ATA and answering machine. I won’t be using the answering machine at all because the Asterisk system provides that for us already. With this new phone you can have 3 calls going at one time (in or out), 2 VoIP calls and 1 normal phone call. On top of that, the system allows for up to 6 VoIP providers to be configured in the system allowing for say 6 incoming VoIP phone numbers + the PSTN number, so 7 numbers in all. Ok, for a home user it’s a bit over the top. However, for me with the Asterisk PABX, the coolest thing to do is create new extension numbers for each handset. What does this give me? I can still setup multiple numbers for each handset, but more to the point I can do nifty things like say, between the hours of 11pm and 7am ring all the phones except the bedroom phone, unless your caller ID says you are someone I really should be taking calls from at that hour of the day.

From the Siemens website they list these as some of the features:


  • Integrated answering machine with up to 30 minutes of recording time
  • Dual mode: easy switch from internet calls to fixed-line calls by single keypress
  • Information services as screensaver* e.g. weather forecast
  • Expandable phone system with multiline calling for up to 6 handsets and 6 SIP accounts from different providers


  • ECO DECT โ€“ for 60% less energy useยน and variable reduction of transmitting power
  • Easy configuration of internet telephony (VoIP) without a PC
  •**: Worldwide free of charge calls between supporting VoIP phones
  • Up to 3 calls in parallel: 2 VoIP calls and 1 fixed-line call with multiple handsets
  • E-mail notification with time, date and subject
  • Instant Messaging (buddy list, chatting, presence status)
  • Increased virus protection thanks to protected operating system
  • Convenient handsfree talking in brilliant sound quality
  • CLIP** / CNIP**
  • Illuminated display with 4096 colors and 128 x 128 pixels
  • Intuitive icon-based menu
  • SMS** with up to 612 characters
  • Phonebook for up to 150 names and numbers

Some of the very nice features that I liked are simple things.. you can upload your phone directory from either a TSV file or in standard VCARD format.. once you’ve uploaded all your phone numbers to one phone you can then share that out with all the phones. Most other DECT phones don’t have this, certainly not the upload from a PC, and not many support the ability to send out all the numbers to the other phones.

Some of the annoyances I’ve found with this system so far:

  • Very short and unrealistic timeout for the browser based management interface
  • The timeout for the browser interface seems to be around 1-2 mins which means that while making changes and testing those changes and tweaking things on the PABX side you are logged out and have to get back in and navigate back to the page you were working on.
  • Inflexible dial plan editor
    • You can add routing overrides to the dial plan to direct certain numbers or ranges out over various VoIP providers or the PSTN line, but you can’t use proper standard dial plan patterns.
    • The phone has “local” emergency numbers hard coded to use the PSTN only, local being based on the country of sale, so in the UK it would be 999, in North America it would be 911. While making sure those numbers route over PSTN is good you should also be allowed to change that since VoIP providers are having to accommodate emergency numbers.
  • No way to backup your configuration of the base station. I’ve already experienced when this would have been nice. I used the website portal for configuring your RSS feeds to the phone and ended up using a feed it didn’t like. That resulted in the device going into an endless reboot loop. I had to factory reset the device to recover meaning that not only had it lost all my settings but I also had to re-register all the handsets again.
  • You can upload a telephone directory to the handsets, but only one at a time. There is no way to blast the same telephone directory to all handsets at one time. There is also no way to just send the list to a web address or have the base station fetch the file/URL on some interval. Maybe a bit advanced for your average home user, but I’m not average ๐Ÿ™‚
  • Most annoying I think however is the constant “phone home” at the device does to the Siemens Gigaset portal. I really must capture some of that traffic and try to see what exactly is transmitted and what triggers it if I can work it out, for example does it “phone home” after I finish a call to someone? If it does what does it send?
  • Some very positive things about the phone system as well, it’s OpenSource. You can download the source code for the system including tools to build it. I assume the phone base and handsets are running embedded Linux.

    I’ll wrap this up now and post more updates as I use the phone more and more. We’ve had loads of compliments on how much better the phone sounds now, so that’s a big plus. The connections are so much more clear and cleaner with not as much jitter and echo.

    More later on this.

    2 thoughts on “New phones at home..”

    1. Hi Jan,

      You do this via the web interface.
      1) Login
      2) Goto Settings
      3) Goto Telephony
      4) Goto Connections

      Here you simply configure the additional SIP Providers and activate it.

      Then follow steps steps 2 and 3 above but this time goto “number assignment” under the Telephony menu. Toggle which phones should get incoming calls from which SIP providers. You can select all phones get all incoming calls or only certain ones. Likewise, you can select the default outgoing SIP Provider for each phone as well.

      Hope this helps.

    2. hi,

      can you tell me, how to set up multiple handsets with multiple sip accounts? I allready tried to setup 2 sip accounts, but don’t know how to bind one sip account to one handset and the second sip to second handset..

      Thank you


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